 
Summary: Ch&mical Physics 45 (1980) 249260.. 
Q NorthHolland Publishing Company
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AN ANALYTICAL APPROXIMATIkN FOR THE NUMBER OF STATES
ALdNG THE REACTION COORDINATE*
Noam AGMON
Department ofPhysical Chemistry, The Hebrew Unitiersity,
Jerusalem, Israel
Received 21 May 1979
A variant of a new empirical method, enables one fo express a collinear triaromic potential energy surface as a
Family of Morse curves along "natural" bond order coordinates orthogonal to the reaction coordinate. The procedure
depends on a single adjustable parameter which is related to the barriers height. Because an analytical expression for
the number of vibrational states of a Morse oscillator is available, one has an analytical approximation for the
number of states along the reaction coordinate. The extrema in the number of states are utilized in various versions of
classical microcanonical variational transition state theory (among which is a new version, which is in better agree
ment with dynamical results), to estimate the probability of a coliinear reaction, as a function of the total energy. The
analytical expressions are also used to analyze the origins orthe maximum and minima in the number of stares.
1. Introduction
